Industrial utilization of plastics, particularly the so-called engineering thermoplastics, has greatly increased over the past several decades. These materials have found their way into such diverse applications as home and office furniture, airplane interiors, cabinetry and casing for electronic and computer systems and various components for automobiles, machines and cookware, inter alia.
Designers employing the plastic materials place a high premium on fire retardancy since accidental fires continue to extract a heavy toll on life and property. In this regard, the thermoplastic and thermosetting resins are less than satisfactory due to their organic (i.e., inherently combustible) nature. This deficit has been addressed, most notably by incorporating various halogen or phosphorous fire retardant compounds in the plastic composition. A hydrated metallic compound, such as a hydrated alumina filler can also be used as fire retardant component, either by itself or in combination with the aforesaid compounds. Unfortunately, such tactics present disadvantages of their own in that the addition of such fire retardant components generally detracts from the desirable mechanical properties of the plastics. Thus, for example, it is known that phosphorus-based fire retardant additives enhance the fire retardant character of various plastics when incorporated therein. Such modified products can achieve a desirable V-0 rating on a standard Underwriters Laboratories UL-94 flame test, but it has been found that the amounts of additive required severely degrade the impact resistance of the compositions relative to the virgin resins.
The need for modified plastic systems which place less reliance on the above mentioned conventional means to achieve fire retardant properties has been partially addressed, as exemplified by the disclosure of Romenesko et al. in a copending application for patent Ser. No. 906,165, filed on Jun. 29, 1992 and hereby incorporated by reference. In this disclosure, the use of a silicone polymer powder to modify organic resins resulted in systems which exhibited significantly lower rates of heat generation and reduced smoke and carbon monoxide formation relative to the unmodified controls. And, as pointed out in the application to Romenesko et al., it has been well documented that these are the predominant elements responsible for death and injury in a real fire situation.
All of the above mentioned improvements in the modification of plastic resins notwithstanding, there is still a need for plastic materials having a high degree of fire retardancy while still retaining good mechanical properties.